Air conditioning system



A. B. SIMON 2,252,142

AIR conm'rionme sYsTE M Filed Oct. 3, 1938 lhwentor attorney Patented Aug. 12, 1941 NITED sTTES PATENT OFFICE AIR CONDITIONING SYSTEM Andrew E. Simon, Cleveland, Ohio, assignor to 'M nneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application Uctoher a, 1933, Serial No. 232,943 a 13 Claims.

auditoriums it has been found that the air tends to stratify, the hot air collecting adjacent the ceiling and colder air being adjacentthe floor line. This is quite objectionable as it causes overheating of-the balcony and underheating of the orchestra. One manner for avoiding this undesirable result is by limiting the temperature of the hot air being discharged into the space so that it does not rise rapidly. This permits the air temperature throughout the entire space to be substantially equalized. However, this limiting of the discharge air temperature during extreme cold weather may cause underheating of the space. Also this limiting of the discharge air temperature limits the rate of heat supply to the space and consequently prolongs the time necessary for heating the space from a low value desired when the space is unoccupied to the higher value necessary when the space is occupied.

It is an object of this invention to provide a control system for applications of this type which prevents the temperature of the heated air delivered to the space from rising above a predetermined value when the space temperature is at the desired value thereby avoiding stratification of the air within the space, and which automatically raises the temperature of the delivered air to a higher value upon fall in space temperature from the desired normal value. More broadly stated, it is an object of this invention to provide a control system in which a space condition controller controls a condition changer subject to the control of a high limit controller but which reduces the effect of the high limit.

controller as the space condition varies from the desired vlaue.

A further object of this invention is the provision of a condition controlling system in which.

"a space condition controller controls a condition changer subject to high and low limit controllers and which places one of the limit controllers out of which diagrammatically indicates an air blast heating system having a control system embodying this invention. a I Reference character l indicates an air conditioning chamber which contains a heating coil 2. This chamber is connected by a return air duct 3 to a space t which is being heated. This chamber is also connected to a fresh air duct 5 which supplies air for ventilation purposes. A fan 6 is connected to the other end of chamber l for drawing air across the heating coil 2 and discharging it to the space t through a discharge duct l.

Steam 'or other heating medium may be supplied to the coil 2 by means of a pipe 8 having a valve 9 interposed therein. This valve may be actuated by means of a proportioning motor l0 which may take the form shown and described in the Taylor Patent 2,028,110. This motor is controlled by means of a space thermostat H, a high limit discharge thermostat l2 and a low limit discharge thermostat l3.

Referring to the thermostat ll this thermostat may include a bellows i l which is attached by capillary tube it to a control bulb lli' located within the return air duct 3. The bellows, tube, and'bulb are charged with a suitable volatile fill for causing the pressure withinbellows I l to vary in accordance with changes in return air temperature. The bellows Hi actuates a pair of sliders H and ill. The actuating mechanism for the sliders ill and i8 is diagrammatically illustrated as including an actuating arm I9 which is engaged by bellows Ill and which directly actuates the slider Ill. The slider I8 is actuated in unison with the slider ill by means of an insulated link 20. The slider ll cooperates with a contact strip 2!! and a resistance 22 while slider l8 cooperates with a contact strip 23 and a resistance 24. This thermostat III may be so designed and adjusted that whenthe return air temperature is at 72 F. or above, the slider ll engages the left-hand end ofcontact strip 72 while the slider l8 engages the left-hand end of resistance 24. As the space temperature falls below 72 F., the pressure within the bellows .M will decrease which permits a biasing spring 25 to shift sliders l1 and the slider I! will contact resistance 22 and the slider IE will engage the contact strip 23. When the space temperature falls to 68 F., the slider actuating arm 33 is biased against the bellows 30 by a spring 36. -This instrument may be so designed and adjusted as to cause the slider 34 to engage the right-hand end of resistance 35 when the discharge temperature is at or'below 95 F., while causing the slider 34 to engage the left-hand end of resistance 35 when the discharge temperature is at or above 100 F.

The low limit discharge. controller I3 may be This bellows may actuate a bell-crank formed similarly to the controller I2 and includes a bellows 38 which is connected by a tube 39g'toa control bulb 48 located in the discharge duct I; This thermostat also includes a slider 4| which is actuated by bellows 38 and which cooperates with a resistance 42 to form a potentiometer. This controller may be designed and adjusted in a manner to cause the slider 4| to engage the lefthand end of resistance 42 when the discharge temperature is at or above 65? F. while engaging v values of resistances which are connected between terminals R and W and R and B. For example, if equal amounts of resistance are connected between terminals R and W and between terminals R and B, the motor III will assume mid position in which the valve 9 is half open. However, as the resistance between terminals R and B is decreased without corresponding decrease in resistance between terminals R and W, the motor II] will operate in a direction to open the valve 9 i an amount proportionate to the unbalancing of the resistances. Conversely, if the resistance between terminals R and W is decreased without corresponding decrease in resistance between terminals R and B, the motor I0 will operateto close valve 9 an amount proportionate to the unbalancing of the resistances connected across the control terminals.

wire 41 to the slider 34 of the high limit controller I2, and the right-hand end of resistance 35 of this controller is connected by wire 48 to the slider I8 of thermostat I I. With the various controllers in the positions shown, the discharge temperature is above 65 F. and below 95 F., as

indicated by the slider 4| of thermostat I3 engaging the left-hand end of resistance 42, and the slider 34 of the high limit thermostat I2 engaging the right-hand end of resistance 35. The space or return air temperature is approximately 71 F. as indicated by the slider I8 of the thermostatI I. engaging the center of the resistance 24. For this position of slider I8 the slider I1 is engaging the contact'strip 2|. With the controllers in the positions shown, the-terminal R of motor III is directly connected to the slider I8 of thermostat II as follows: terminal R, wire 45, slider 4|, wire 46, slider I'I, contact strip 2|, wire 41, slider 34, and wire 48 t0 slider I8. It will be noted that the contact strip 23 is connected to terminal B of motor III by wires 49 and 58, while the resistance 24 is connected to terminal W of motor III by wires 5| and 52. Therefore with the parts in the positions shown, the slider I8 of thermostat II is connected to terminal R', the resistance 24 is connected to terminal W and the contact strip 49 is connected to terminal This causes the slider I8 to divide the resistance 24, the left half of this resistance being connected between terminalsR and W, and the right half of this resistance being connected between terminals R and B. The resistance connected between terminals R and W is therefore equal to theresistance connected between terminals R and B, which causes the motor III to assume mid position in which the valve 9 is half open. If the space temperature should increase, the slider I8 of thermostat II will shift to the left along resistance 24 which decreases the portion of this resistance connected between terminals R and W and increases the portion of this resistame connected between terminals R and B. This will cause the motor III to close valve 9 an amount proportionate to the position of the slider I8 on resistance 24. When the space temperature reaches 72 F. terminals R and W of the motor III will be substantially short-circuited thus causing the motor In to place valve 9 in closed position. Upon decrease in space temperature, the slider I8 will be shifted to the right across resistance 24 thus decreasing .the portion of this resistance which is connected between terminals R and B while increasing the portion connected between terminals R and W. Thiswill cause motor III to open valve 9proportionately to the fall in space temperature. When the space temperature falls to 70 F., the slider.I8-will engage the right-hand end of resistance 24 forv opening valve 9 wide.

From the foregoing description it should be apparent that when the discharge temperature is between the settings of the limit controllers I2 and I3, the potentiometer controller of thermostat II formed of slider I 8, resistance 24, and contact strip 23 will be placed in complete control of the valve motor III, and this controller will operate to open the valve graduatingly upon fall in space temperature and to close'thevalve graduatingly upon an increase in space temperature.

In mild weather only a small amount of heat will be required for maintaining the space temperature at the desired value, which may cause the thermostat II to tend to close valve 9 to such an extent that the discharge temperature falls below 65 F. This condition would be undesirable as the discharge of air at this temperature might cause uncomfortable drafts to occur in certain portions of the space being heated. In the event that the discharge temperature does fall below 65 F., the slider 4 I of the low limit thermostat I3 will move to the right across resistance 42. It will be noted that the circuit previously traced between terminal R of motor I8 and the slider I8 of thermostat II passes through the slider 4|. Consequently, as the slider 4| travels to the right across resistance'42, a portion of this resistance is inserted into the circuit between terminal R of the motor and the slider I8 of thermostat II. This inserting of resistance into this circuit decreases the effect of the slider I8 upon the motor temperature of the discharge air.

I0. It will also be noted that the right-hand end of resistance 4| is connected by wire 53 and wire 50 to terminal B of motor I. Consequently when the slider. 4| is in the position shown, the entire resistance 42' is in circuit between terminals R and B of motor Ill. The slider 4| in shifting to the right along resistance 42, acts to decrease the portion of thistresistance between terminals R and B. Therefore it will be seen that as the discharge temperature falls below 65 F., the slider 4i travels to the right across resistance 42 which decreases the efiect of the thermostat upon motor I0, and also decreases the resistance connected between terminals R and B. This will cause the motor III to open valve 9 for supplying heating medium to the coil 2 even though the space thermostat it may be satisfied. lnjtlris manner the low limit controller It acts to.. pre-.

space such as an auditorium at high temperature,

this high temperature air will rise to the ceiling thus overheating the balcony while underheating the orchestra. By limiting this temperature, this undesirable stratification of the air within the space being heated is avoided.

In the event that discharge air shouldrise above 95 F. due to the space thermostat ll opening the valve 9 too widely, the slider 34 of the high limit thermostat It will shift to the right along resistance 35. This will interpose a portion of the resistance 35 into circuit with the slider N3 of ther- It has been mostat H, and thus decrease the effect of this the position shown the entire resistance is con-- nected between terminals R and W of motor ill. The slider St in shifting to the right along this resistance therefore inserts a portion of this re sistance in series with the thermostat Ill, and also decreases the portion of this resistance which is connected between terminals R and W of motor it. This causes this motor to operate in a direction for closing valve 9 for thus reducing the In this manner the high limit thermostat l2 operates to prevent the space thermostat from opening the valve 9 to such a point that the discharge air temperature rises above a predetermined value. As pointed out above, this prevents stratification of the air within the space being heated and thus provides for evenly heating such space.

When the space has been unoccupied and is being brought up to temperature for occupancy, the limiting of the air discharge temperature to a low value such as 95 or 100 F. will prevent the ture falls below 70 F. the slider ll of thermostat l l vill begin shifting to the right along resistance 22. This will interpose a portion of the resistance 22 into circuit between terminal R of motor Hi and the slider 34 of the limit controller l2. This is due to the circuit between terminal'R of motor Ill and the slider 34 of thermostat l2 being as follows: terminal R, wire '45, slider 4|, wire 46, slider resistance 22, contact. strip 2| and wire 41 to slider 34. This interposing of resistance between terminal R of motor i0 and the slider 34 of the limit controller '|2 will decrease the effect of this limit controller upon the motor -||I.

It will be noted that the right-hand end of resistance 22 is connected by wires 55 and 5!] to terminal B. Due to the slider i1 being directly connected to terminal R, movement of this slider to the right along resistance 22 will decrease the portion of this resistance which is connected between terminals R and B. When the return air temperature falls to 68 F., a short circuit between terminals R and B of motor I!) will be established as follows: terminalR, wire 45, slider 4|, wire 46, slider ll, wire 55, and wire 50 to terminal B. This will cause the valve ill to be wide open irrespective of any action of the high limit controller l2. It will therefore be seen that as the space temperature falls below 70 F., the high limit controller l2 will gradually be cut out of the motor control circuit which renders it ineffective to prevent'the discharge air temperature from rising above 95 F. Thus fall in space temperature between 70 F. and 68 F.

' acts to graduatingly raise the control point of the high limit thermostat l2 and when the space temperature falls to 68 F. the valve 9 will be wide open irrespective of the discharge temperature.

When the space is being heated up from a shutdown temperature to occupancy temperature, the high limit controller l2 will be prevented from having any effect upon the valve 9 so long as the space temperature is below 68 F. Thus during this .period the valve 2 is wide open for supplying a maximum amount of heat to the space. As the space temperature rises above 68 F. the discharge thermostat [12 will .be graduatingly replaced into the control circuit for thus permitting it to assume its function of limiting the discharge air temperature. This will cause the temperature of the discharge air to graduatingly lower as the space temperature reaches 70 F., and when the space temperature reaches 70 F. the thermostat l2 will be conditioned for preventing the discharge air temperature from rising above the control point of this thermostat. uatingly replacing of the thermostat l2 into control as the space reaches the desired value is very desirable for it acts to reduce stratification within the heated space and cause it to be evenly heated at the time the occupancy temperature is reached.

It will be noted that a resistance 55 is con- ,nected across terminals R and W at the motor ill. The purpose of this resistance is to balance out the control circuit when the various controllersare in their normal positions. It will be 'noted that with the controllers H, M and lit in the positions shown, resistances 22 and 42 are connected between terminals R and B while resistance 35 is connected between terminals R and W. Thus two resistances are connected between terminals R and B and only one between terminals R and W. By providing the additional resistance 56 which' is of the same value as the other resistances, the circuit is completely balanced.

. From the foregoing description it will be apparent that this invention provides a control system which controls the supply of heat to a space in accordance with space temperature and. also This grad- I sive to the condition of the controls the supply of heat in a manner to prevent the temperature of the discharge air from falling below a predetermined low value or rising above a predetermined high value, and which automatically raises the high limit value in the event that the space temperature falls below the setting of the space thermostat. It will also be apparent that the system of 'his invention pro-- vides for supplying heat to the space at maximum rate when the space is being heated for occupancy, and graduatingly places the limit con-' troller in control as the space temperature approaches the desired normal value for thus avoiding stratification of the air at the time that the normal temperature is reached.

While throughout this description I have mentioned definite values of temperature at which the controls may operate, it will be understood that these values are illustrative on y and may be varied for difierent applications and installations embodying this invention. Also while the invention has been described as applied to a heating system, it will be apparent that it is of broader scopeand may be utilized in systems other than heating systems and forcontrolling other conditions than temperature. As various modifications of this invention will occur to those of the proportioning type for controlling said condition changer, control line means between said control means and saidmotor means for rendering said control means effective to control said condition changer in a modulating manner,

-a low limit controller of the proportioning type connected into said control line means and responsive to the condition of the medium being supplied to said space for normally preventing the condition of said medium from falling below a predetermined value irrespective of said control means, a high limit controller of the proportioning type connected into said control line means and responsive to the condition oi the medium being supplied for normally preventing the condition of the supplied medium from rising above a predetermined value, and means actuated in response to the condition in 'said space being controlled varying beyond a predetermined value for gradually reducing the efiect of one of said limit controller.

2. In a system for controlling the condition in a space, in combination, means for supplying conditioning medium to said space, condition changing means for controlling the condition of the medium supplied to said space, control means responsive to the condition of the space being controlled, motor means for controlling said condition changer, control line means between said "control means and said motor means for renderfalling below a predetermined value for rendering said high limit controller means inefiective.

3. In a system for controlling the condition in a space, in combination, means for supplying conditioning medium to said space, condition changing means for controlling the condition of the medium supplied to said space, control means responsive to the condition of the space being controlled, motor means for controlling said condition changer, control line means between said control means and said motor means for rendering said control means efiective to control said condition changer,-alow limit controller responsive to the conditions of the-medium being supplied to said space for normally preventing the condition of said medium from falling below a predetermined value irrespective of said control means, a high limit controller responsive to the condition of the medium being supplied for normally preventing the condition of the supplied medium from rising above a predetermined value,

and means actuated in response to the condition in said space being controlled falling below a predetermined value for rendering said high limit controller ineffective to prevent the condition the medium supplied to said space, control meansresponsive to the condition of the space being controlled, motor means for controlling said condition changer, control line means between said control means and said motor means for rendering said control means eifective to control said condition changer, a low limit controller connected into said control line means and responsive to the condition of the medium being supplied to said space for normally preventing the condition of said medium from falling below a predetermined value irrespective of said control means, a high limit controller connected into said control line means and responsive to the condition of the medium being supplied for normally preventing the condition of the supplied medium from rising above a predetermined value, and means actuated in response .to the condition in said space being controlled falling below a predetermined value for rendering said high limit controller inefiective to prevent the condition of said medium from rising above said predeter--v means for rendering said thermostat effective to normally maintain the space temperature within predetermined limits, a high limit thermostat connected to said control line means for noring said control means eifective to 'control said condition changer, a high limit controller connected into said control line means and respondium being supplied for normally preventin the condition of the supplied medium from rising above a predetermined value, and means actuated in response mally preventing said space thermostat from raising the temperature 01'. the temperature changing medium above a predetermined value, and means actuated in response to the temperature in said space falling below a predetermined value for rendering said high limit thermostat 'ineifective.

6. In a system for changing the temperature a high limit thermostat for normally preventing said space thermostat from raising the temperature of the temperature changing medium above a predetermined value, and means actuated in response to the temperature in said space falling below a predetermined value for rendering said 'high limit theremostat ineffective to prevent the condition of said medium from rising above said predetermined value,

7. In a system for changing the temperature of a space, in combination, means for supplying temperature changing medium to said. space, means for varying the temperature of the temperature changing medium supplied, a thermostat responsive to the temperature of thespace being controlled, motor means for controlling said temperature varying means, control line means between said thermostat and said'motor means for rendering said thermostat effective to normally maintain the space temperaure within predetermined limits, a low limit thermostat connected to saidcontrol line means for' normally preventing said space thermostat from reducing the temperature of the temperature changing medium below a predetermined value, a high limit thermostat connected to'said control line means for normally preventing said space thermostat from raising the temperature of the rtemperature changing medium above a predetermined value, and means actuated in response. to the temperature in said space falling below a predetermined value for rendering said high limit thermostat ineffective to prevent the condition the air after passing through said heater and connected into said control line means for normally preventing said space thermostat from reducing the temperature of the air passing to said space below a predetermined value, a high limit the air heated by said heater and connected into said control line means for normally preventing thermostat also responsive to the temperature of v the air passing to said space from rising above a predetermined temperature, and means actuated in response to the temperature in said space falling below a predetermined value for rendering said high limit thermostat inefiective to prevent the temperature of the air passing to said space from risingabove said predetermined value.

10. In a system for heating a space, in combination, heating means for heating a heating medium being supplied to said space, motor means for controllin said heating means, thermostatic means responsive to space temperature, control line means between said motor means and said space thermostatic means, a high limit thermostat responsive to the temperature of the medium being supplied to said space, said high limit thermostat being connected into said control line means and. operative to normally prevent the temperature of the heating medium from rising above a predetermined value irrespective of I changes in space temperature, and means actuof said medium from rising above said predetermin-ed value.

8. In a system 'for heating (a space, in combination, means for passing a stream of air to said space, a heater for heating the air stream, motor means for varying the output of said heater, a-

thermostat responsive to the temperature'of the space, control line-means between said thermostat and said motor means for rendering said thermostat efiective to control said heater, a high limit thermostat responsive to the temperature of the air heated by said heater and connected into said control line means for normally preventing the air passing to said space from rising above a predetermined temperature, and means actuated in response to the temperature in said space falling below a predetermined value for rendering said high limit thermostat ineifective,

93in a system for heating a space, in combination, means forapassing' a stream of airto said space, a heater for heating the air stream, motor means for varying the output of 'said heater, a

' thermostat responsive to the temperature of. the

space, control line means between said'thermostat and said motor means for rendering said thermostat effective to control said heater, a low limit thermostat responsive to the temperature of ated upon fallin space temperature below a predetermined value for rendering said high limit thermostat ineffective to prevent the temperature of the heating. medium from rising above said predetermined value.

llQIn a system for heating a space, in combination, means for passing a stream of air to said space, a-heater for heating the air stream, mo-

tor means for varying the output ,of said heater, a thermostat responsive to the temperature of the space, control line means between said thermostat and said motor means for rendering said thermostat effective to control said heater, a high limit thermostat responsive to the temperaturev of the air heated by said heater and connected into said control line means for normally preventing the air passing to said space from rising above a predetermined temperature irrespective of variations in space temperature, and means actuated in response to the temperature in said space falling below a predetermined value for rendering said high limit thermostat ineffective to prevent the temperature of the air passing to said space from rising above said predetermined value.

12'. In a system for heating a space, in combination, means for passing a stream of air to said space, a heater for heating the air stream, electromagnetic means for varying the output of said heater, a contro1 circuit for said electromagnetic means, thermostatic current controlling means responsive to the temperature of said space and connected into said control circuit for controlling said heater in a manner to maintain the space temperature within predetermined limits, a low limit thermostatic current controlling means connected into said control circuit for preventing the temperature of the air passing to said spacefrom. falling below a predetermined value, a high limit thermostatic current controlling means connected into said control circuit for normally preventspace from rising above a predetermined value,

and current controlling means connected into ing the temperature of the air passing to said rendering said high limit current controlling means ineffective to prevent the temperature of the air passing to the space from rising above said predetermined value. I

' 13. In a system for heating a space, in combination, means for passing a stream of air to said space, a heater for heating the air stream,.e1ectromagnetic means for varying the output of said space fromrising above a. predetermined value,

and current controlling means connected into said control circuit and eflective upon fall in space temperature to a predetermined value for heater, a control circuit for said electromagnetic means, thermostatic current controlling means responsive to the temperature of said space and connected into said control circuit for controlling said heater in a manner to maintain the space rendering said high'limit current controlling means ineffective to prevent the temperature of the air passing to the space from rising above said predetermined value.

ANDREW B. SIMON. 

